﻿#region License

//-----------------------------------------------------------------------
// <copyright>
// The MIT License (MIT)
// 
// Copyright (c) 2014 Kirk S Woll
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of
// this software and associated documentation files (the "Software"), to deal in
// the Software without restriction, including without limitation the rights to
// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
// the Software, and to permit persons to whom the Software is furnished to do so,
// subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
// FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
// COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
// IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
// </copyright>
//-----------------------------------------------------------------------

#endregion

using System.Collections.Generic;

namespace System.Linq
{
    /// <summary>
    /// Defines an indexer, size property, and Boolean search method for data structures that map keys to <see cref="T:System.Collections.Generic.IEnumerable`1"/> sequences of values.
    /// </summary>
    /// <typeparam name="TKey">The type of the keys in the <see cref="T:System.Linq.ILookup`2"/>.</typeparam><typeparam name="TElement">The type of the elements in the <see cref="T:System.Collections.Generic.IEnumerable`1"/> sequences that make up the values in the <see cref="T:System.Linq.ILookup`2"/>.</typeparam><filterpriority>2</filterpriority>
    public interface ILookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>
    {
        /// <summary>
        /// Gets the number of key/value collection pairs in the <see cref="T:System.Linq.ILookup`2"/>.
        /// </summary>
        /// 
        /// <returns>
        /// The number of key/value collection pairs in the <see cref="T:System.Linq.ILookup`2"/>.
        /// </returns>
        int Count { get; }

        /// <summary>
        /// Gets the <see cref="T:System.Collections.Generic.IEnumerable`1"/> sequence of values indexed by a specified key.
        /// </summary>
        /// 
        /// <returns>
        /// The <see cref="T:System.Collections.Generic.IEnumerable`1"/> sequence of values indexed by the specified key.
        /// </returns>
        /// <param name="key">The key of the desired sequence of values.</param>
        IEnumerable<TElement> this[TKey key] { get; }

        /// <summary>
        /// Determines whether a specified key exists in the <see cref="T:System.Linq.ILookup`2"/>.
        /// </summary>
        /// 
        /// <returns>
        /// true if <paramref name="key"/> is in the <see cref="T:System.Linq.ILookup`2"/>; otherwise, false.
        /// </returns>
        /// <param name="key">The key to search for in the <see cref="T:System.Linq.ILookup`2"/>.</param>
        bool Contains(TKey key);
    }
}